Who gives more, the haves or the have-nots?

It's one of life's great ironies – those who have more give less. Research shows that the wealthy are quite a bit more, well, greedy than the poor. One study found that households earning less than $25,000 a year donated an average of 4.2 percent of their incomes while those making $75,000 or more gave away 2.7 percent. Another study found that the poor have a stronger sense of empathy and connectedness to others. The rich, by contrast, lacked compassion and tended to shield themselves from the needs of others. So are the wealthy just inherently selfish, or is there something about money that brings out the worst, but not the wallet?